The knowledge of the central role of platelets in the pathogenesis of acute coronary syndromes, on the one hand, and the fact that aspirin is a weak antiplatelet agent on the other, have led to an intensive investigational activity in antiplatelet drugs in the last years. Actually, the literature in the last two years is inundated with studies on the use of platelet IIb/IIIa receptor blockers in different clinical settings. Agents that block the IIb/IIIa platelet receptor have shown to be useful in improving prognosis of patients with acute coronary syndromes, especially in those undergoing percutaneous coronary revascularization procedures. However, their potential risk of bleeding and their high cost have prevented them from being applied universally and routinely. Furthermore there are still some unclear issues regarding the use of these drugs such as their correct dosage, the optimal duration of treatment and the direct comparison of the efficacy of different types of IIb/IIIa blockers available. On the other hand, oral IIb/IIIa antagonists have not improved the efficacy of aspirin to date and, moreover, they have been proven to be unsafe. Finally, it is necessary to identify those patients who will obtain the greatest benefit from the treatment in order to avoid the unnecessary risks and costs that would be derived from their universal use.